Guardiera S, Bock O, Pongratz H, Krause W. Acceleration effects on manual performance with isometric and displacement joysticks. Aviat Space Environ Med 2007; 78:990–4. Background: We have shown before that novice human subjects produce exaggerated isometric forces when exposed to three times normal terrestrial acceleration (+3 G_z), and that this deficit is compensated by intensive training in +3 G_z. We now investigate whether training in normal terrestrial gravity (normal G) is also effective. We further examine whether subjects in +3 G_z produce not only exaggerated forces, but also exaggerated hand displacements. Methods: Experiments were conducted in the stationary (normal G) or rotating (+3 G_z) gondola of a man-rated centrifuge. With their dominant hand, subjects produced either forces using an isometric joystick, or hand displacements using a regular joystick. Response directions and magnitudes were prescribed visually. In practice trials, subjects received continuous visual feedback about their performance, while in test trials they did not. Results: Subjects produced exaggerated forces in +3 G_z, whether or not they previously practiced the task in normal G. In contrast, subjects did not produce exaggerated hand displacements in +3 G_z. Discussion: Exaggerated force production in +3 G_z is not overcome by task practice in normal G, as opposed to task practice in +3 G_z. This might be an indication that pilot training should contain extended practice of force production during phases of increased gravity (+G_z) to avoid motor deficits during flight maneuvers inducing +G_z. Furthermore, the control of isometric and regular joysticks seems to be based on partly distinct neural mechanisms, with different +G_z dependence. Thus, against the background of motor performance during +G_z, regular sticks might be favorably compared to isometric sticks in high-performance aircrafts.